1. Field of the Invention
This invention relates to apparatus for mounting electronic circuits, and particularly electronic circuits implemented on circuit boards in the cabinets or enclosures of electric power equipment. More particularly, it relates to a snap-in and quick release edge mount for such circuit boards.
2. Background Information
Electronic circuits for electric power equipment are typically implemented on multiple circuit boards which are in turn mounted in a metal equipment cabinet or enclosure. Various arrangements have been utilized to mount the circuit boards. In smaller enclosures, the multiple circuit boards are stacked horizontally or vertically by sliding them into fixed slots formed along facing top and bottom or opposed side walls, respectively, in the enclosure and locking them in place such as by rotatable clamps or other locking devices. Such stacked (or piggy backed) mounting can make plugs on the boards for test equipment and related components inaccessible.
Electronic circuits for some electric power equipment, for instance exciters for large generators, operate at substantial voltages which must be isolated. A known arrangement for mounting the electronic circuit boards for such applications is shown in FIGS. 1 and 2. Two electronic circuits 1a and 1b are implemented on circuit boards 3a and 3b, respectively. The circuit boards 3a and 3b are secured in spaced parallel relation to electrically insulative mounting panels 5a and 5b by electrically isolated standoffs 7a and 7b. 
Each of the mounting panels of 5a and 5b is secured to a panel 9 and an electrical equipment enclosure (not shown) by an L-bracket 11a and 11b, respectively. Each bracket 11a, 11b has a first flange 13 which is bolted to the panel 9 and a second flange 15 at right angles to the first flange and to which the associated mounting panel is secured.
Thus, the mounting panels 5a and 5b are cantilevered outward from the panel 9 by the L-brackets 11a and 11b. The electric circuits 1a and 1b are isolated from one another by mounting their respective circuit boards 3a and 3b on outward facing sides of the mounting panels. The standoffs 7a and 7b further increase the creep distance between the two circuits.
While the arrangement of FIGS. 1 and 2 provides easy accessibility to the electronic circuits and good electrical isolation for the substantial voltages in the circuits, there are some drawbacks. Vibrations caused by internal harmonics, transport or seismic activity increases the probability of failure or malfunction. While bracing 17 between the mounting panels stiffens the structure, there is still room for improvement.
There is a need therefor for an improved apparatus for mounting electronic circuits in electronic power equipment enclosures which provides a compact arrangement with ready access to, and adequate isolation for the elevated voltages in, the circuits while also providing suitable isolation from vibration.
There is a further need for such mounting apparatus which provides for easy installation and removal of the circuits, yet is simple, easily fabricated, and economical.
These needs and others are satisfied by the invention which is directed to a user-friendly, slide-in/slide-out, self-locking apparatus for mounting electronic circuits in electric power equipment enclosures. The apparatus includes a bracket comprising a pair of planar legs each having a base section and a free section compliantly cantilevered laterally outward from the base section. Each free section has at least one longitudinally extending slot, at least one of which, has a closed forward end. The bracket also includes mounts mounting the base sections of the pair of planar legs to the electrical power equipment enclosure with the free sections in spaced facing alignment and with the at least one longitudinal slot in each free section aligned. The apparatus further includes an electronic assembly comprising a planar member and an electronic circuit supported by the planar member. The planar member has opposite side edges spaced apart to spread the compliantly cantilevered free sections of the bracket apart and engage the at least one longitudinally extending slot in each free section. The planar member has a latching surface engaging the closed forward end in the one slot to releasably latch the planar member to the bracket with the opposite side edges of the planar members seated in the longitudinally extending slots in the free sections of the planar legs. The free sections of the planar legs are compliantly deflectable away from each other for unlatching and removal of the planar member.
Preferably, the base sections of the two planar members are integral to form a single piece bracket. Also preferably, one of the opposed edges of the planar member has a shoulder forming the latching surface.
The electronic circuits are implemented on a circuit board which can be the planar member which is slid into the slots in the bracket for direct mounting. However, in the most preferred form of the invention, the planar member is a separate, preferably electrically insulative member, and the circuit board is mounted on the panel member, preferably by electrically insulative standoff mounting members.
Two electronic assemblies can be mounted by a single bracket by providing a pair of longitudinally extending slots in the free sections of the pair of planar legs. Again, the circuit boards can be directly inserted into the slots, but preferably, insulative panel members supporting the circuit boards are secured in the pair of slots in the bracket. In this arrangement, the circuit boards can be mounted on the outwardly facing sides of the two panel members to provide additional isolation between the circuits.
The longitudinally extending slots in the free sections of the planar legs of the bracket can be through slots. In addition, the free sections can have divergent terminal sections in which the longitudinally extending through slots terminate to form support surfaces for the side edges of the planar member. At least one of the terminal sections can diverge at an acute angle to form a camming surface. The associated side edge of the panel member can have a complimentary camming surface which engages the camming surface on a divergent terminal supportion to spread the free sections apart as the panel member is inserted in the longitudinally extending slots. In a particularly advantageous arrangement, this side edge of the planar member can have a tab with the complimentary camming surface on a rearward facing edge of the tab and the latching surface for locking the panel member in the bracket on a forward edge of the tab.
The longitudinally extending slots in the free sections of the planar legs of the bracket can terminate short of the base sections. In this case the opposite side edges of the planar member have notches extending from a rear edge of the planar member to form an offset section of the side edge which seats on the free section of the planar leg between the longitudinally extending slot and the base section. These notches can be sized and the longitudinally extending slots can be positioned so that when the panel member is latched in the bracket, the rear edge of the panel member seats against the base sections of the planar legs.